How do you change the value inside of a textfield flutter?

Simply change the text property

    TextField(
      controller: txt,
    ),
    RaisedButton(onPressed: () {
        txt.text = "My Stringt";
    }),

while txt is just a TextEditingController

  var txt = TextEditingController();

The problem with just setting

_controller.text = "New value";

is that the cursor will be repositioned to the beginning (in material's TextField). Using

_controller.text = "Hello";
_controller.selection = TextSelection.fromPosition(
    TextPosition(offset: _controller.text.length),
);
setState(() {});

is not efficient since it rebuilds the widget more than it's necessary (when setting the text property and when calling setState).

--

I believe the best way is to combine everything into one simple command:

final _newValue = "New value";
_controller.value = TextEditingValue(
      text: _newValue,
      selection: TextSelection.fromPosition(
        TextPosition(offset: _newValue.length),
      ),
    );

It works properly for both Material and Cupertino Textfields.